1. Field of the Invention
The present invention relates to a method for producing an image-forming apparatus using electron-emitting devices.
2. Related Background Art
The conventionally known electron-emitting devices are roughly classified under two types using thermionic emission devices and cold-cathode emission devices. The cold-cathode emission devices include field emission type (hereinafter referred to as "FE type") devices, metal/insulator/metal type (hereinafter referred to as "MIM type") devices, surface conduction electron-emitting devices, and so on. Examples of the FE type devices known include those disclosed in W. P. Dyke & W. W. Dolan, "Field emission," Advance in Electron Physics, 8, 89 (1956) or in C. A. Spindt, "PHYSICAL Properties of thin-film field emission cathodes with molybdenum cones," J. Appl. Phys., 47, 5248 (1976), and so on. Examples of the MIM type devices known include those disclosed in C. A. Mead, "Operation of Tunnel-Emission Devices," J. Appl. Phys., 32, 646 (1961), and so on. Examples of the surface conduction electron-emitting devices include those disclosed in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965), and so on. The surface conduction electron-emitting devices utilize such a phenomenon that electron emission occurs when electric current is allowed to flow in parallel to a thin film of a small area formed on a substrate. Examples of the surface conduction electron-emitting devices reported heretofore include those using a thin film of SnO.sub.2 by Elinson described above [M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965)], those using a thin film of Au [G. Dittmer: "Thin Solid Films," 9, 317 (1972)], those using a thin film of In.sub.2 O.sub.3 /SnO.sub.2 [M. Hartwell and C. G. Fonstad: "IEEE Trans. ED conf.," 519, (1975)], those using a thin film of carbon [Hisashi Araki: Shinku (Vacuum), Vol. 26, No. 1, p22 (1983)], and so on.
The surface conduction electron-emitting devices described above are simple in structure and also easy to manufacture, and thus they have such an advantage that many devices can be arrayed across a large area. Research has been done on various applications taking advantage of this feature. For example, such applications include charged beam sources, display devices, and so on. An example of the application with an array of many surface conduction electron-emitting devices is an electron source in which surface conduction electron-emitting devices are arrayed in parallel, the both terminals of the individual devices are connected by respective wires (which are also called common wires) in each row, and many rows are arrayed, as described hereinafter. (Reference should be made, for example, to Japanese Laid-open Patent Application Nos. 64-031332, 1-283749, 2-257552, and so on.) Particularly, in the field of the image-forming apparatus such as the display devices, plane type display devices using the liquid crystal are recently becoming widespread, taking the place of CRT. However, they are not of the self-emission type, and thus they have the problem of having to include a back light, for example. Therefore, development of a self-emission type display device has long been desired heretofore. An example of the self-emission type display device is an image-forming apparatus which is a display device including a combination of an electron source having many surface conduction electron-emitting devices formed therein with a fluorescent member for emitting visible light by electrons emitted from the electron source. (Reference should be made, for example, to U.S. Pat. No. 5,066,883.)
In the plane type image-forming apparatus described above, an electron-source substrate with a plurality of electron-emitting devices arrayed thereon and an image-forming member with a fluorescent member etc. therein are disposed opposite to each other with a vacuum section in between. The above image-forming apparatus displays an image in such a manner that a scanning signal and/or a modulation signal is applied to the electron-emitting devices formed in the electron-source substrate to make each electron-emitting device or some electron-emitting devices emit electrons and that the electrons are accelerated by the anode voltage Va of several hundred V to several kV or more applied to the image-forming member to collide with the fluorescent member, thereby achieving emission of light therefrom.
The plane type image-forming apparatus described above, however, sometimes suffered a significant luminance drop or a dot or line defect in a display image in the early stage of operation. One of causes of these luminance drop and occurrence of defect is occurrence of vacuum discharge and characteristic degradation of electron-emitting device caused by vacuum deterioration (increase in pressure) in a vacuum panel. This vacuum deterioration in the vacuum panel takes places as follows; with actuation of the image-forming apparatus, electron beams start to irradiate the fluorescent member and metal back in the image-forming member, and the panel components including the wires, electrodes, electron-emitting devices, and so on in the electron-source substrate to cause desorption of adhesive gas molecules (or atoms) and the desorption of gas is also enhanced by impact of ions generated therewith, so that the gas thus generated degrades the vacuum (or increases the pressure) in the vacuum panel.
Conceivable countermeasures against the vacuum deterioration are "increasing evacuation performance" and "decreasing a degassing amount from each panel component."
For the former, it is conceivable to mount a getter pump (capture vacuum pump) of a sufficient capacity. In the conventional display devices kept in vacuum inside, such as the CRT, there are little spatial constraints on placement of the getter pump, so that the getter pump can be formed in a wide area. In the case of the CRT, a ratio of the surface area to the volume in the vacuum container was also small, and a sufficient vacuum was thus able to be maintained therein. In the case of the above plane type display devices, there are, however, many spatial constraints on placement of the getter pump, and normally, the getter pump is often formed in a limited area near the panel edge apart from the image display area. Since in the plane type vacuum container the distance to the image display area was very large with respect to the height in the container, there were issues that it was not easy to assure a sufficient exhaust conductance of the getter pump and that it was not easy to achieve sufficient evacuation of local degassing in the display device in particular.
For the latter, a conventional process employed was an evacuation baking process at high temperature to reduce the degassing amount from the panel components. However, normal baking at hundred and several ten .degree. C. is insufficient, and thus it cannot be said that this baking is a good solution to the aforementioned problem. Baking at higher temperatures will result in exclusion of use of members not resistant to the vacuum baking at the higher temperatures, i.e., members experiencing chemical reaction, alloy formation, cohesion of thin film, etc., and combinations thereof as the components used in the display device, so as to increase constraints on the structure of the display device, and it is thus not preferred.